Patients with impaired renal function are likely to have an unfavorable sodium balance and have hyperphosphatemia, since the kidney can no longer excrete the sodium and the phosphate in sufficient amounts. In addition, imbalances occur in the hormonal control of mineral and electrolyte balance. Sodium intake in the intestine leads secondarily to water retention in the body tissue, to a higher blood volume and to hypertension, which aggravates the renal disease. Excessively high serum phosphate levels lead to atherosclerotic vessel wall changes with increased risk of cardiovascular events such as stroke or myocardial infarction. New developments are aimed at inhibitors of sodium intake in the intestine or phosphate intake in the intestine. A substance that inhibits the NHE (Na++/H+ exchange) transport mechanism as set forth in patent publication number US 2012/0263670 leads to a significant reduction in sodium resorption in healthy rats, which is documented by the reduction of sodium excretion in the urine. According to the literature of Labonte et al., this group of substances, as set forth in patent publication number US 2012/0263670, leads to a reduction in sodium excretion through reduced sodium intake by 0.3 mmol compared to a control group and also to a reduction of phosphate excretion in initial pre-clinical in vivo studies in rats in an active compound co-feed mixed test in healthy animals (compare FIG. 4A and 4B in Labonte et al., 2014, Journal of the American Society of Nephrology 26, online publication doi: 10.1681/ASN.2014030317). This medicinal product according to Labonte et al., in a study of healthy rats, 2014, also leads to a minimal reduction in the phosphate resorption in the intestine and thus a reduction in urine excretion, in a study in healthy rats. However, the effect of this substance according to Labonte et al. 2014 does not cause a significant reduction in serum phosphate levels. According to Labonte, an increase in the dose or the use of a substance with a stronger effect leads to severe diarrhea. This shows a narrow therapeutic range of the substances according to Labonte et al., set forth in patent publication number US 2012/0263670. A substance which can simultaneously significantly reduce the serum phosphate level by inhibiting gastrointestinal resorption and which can inhibit sodium resorption and is not associated with increased stool volume and diarrhea is not known with this pronounced effect such as for the substance according to the invention here according to Example 1 and Example 2.